With the advent of spring, many people have symptoms such as itchy nose and runny nose. Obviously, I don't have a cold, but I sneeze and cough constantly. Some people also have problems with itching eyes, redness of skin, rash and so on. At this time, be highly vigilant. You may be "attacked" by allergies. The World Health Organization has listed allergic diseases as one of the key research and prevention diseases in the 21st century. According to a report released by an organization, 30% to 40% of people in the world are troubled by allergies, which has become a public health problem with wide impact. So why are people allergic? What is the substance that makes people allergic? In response to the above problems, the reporter of science and technology daily interviewed relevant experts. The immune system "defends excessively" causes allergy "Allergic diseases are also known as allergic diseases, which is commonly known as allergies. Allergies are the over reaction of the human immune system to some harmless substances." Liu Ruiling, deputy chief physician of the Department of allergy of the General Hospital of Tianjin Medical University, said in an interview with science and Technology Daily that the human immune system is responsible for resisting the invasion of foreign bacteria, viruses and foreign bodies. They will distinguish substances that do not belong to the human body and help the human body "eliminate dissidents" in order to achieve the purpose of self-protection. If the immune system regards normal substances as harmful substances, it will mobilize immune cells in the body to produce immunoglobulin E, cytokines, neuropeptides and other substances to attack them. If the reaction of the immune system exceeds its due level, it will cause accidental injury to its normal tissues or organs, resulting in a variety of allergic symptoms. Common allergic diseases include allergic rhinitis, allergic conjunctivitis, urticaria, allergic dermatitis, etc; A serious allergic disease is anaphylactic shock, which can be life-threatening. However, not everyone is allergic. Similarly, when encountering pollen, some people's immune system is "indifferent", but some people's immune system will be "high-energy early warning" and "overreaction". Why? "Allergies often occur in a relatively fixed part of the population. Some people have defects in their innate immune system. Their immune system is different from ordinary people, and they are easy to make actions of 'not distinguishing between friends and enemies and attacking for no reason', which leads to the occurrence of allergies. We call this kind of people with allergic constitution." Liu Ruiling said that allergic constitution has a genetic tendency. If both parents have allergic constitution, the probability of their offspring having allergic constitution is 60% to 80%. "Genetic factors are the internal cause of allergic reactions, but people with allergic constitution do not necessarily have allergies. This is because allergies also need external factors, that is, environmental factors - People's exposure to allergens and other irritants." Liu Ruiling explained that substances that can cause allergic reactions are called allergens. When people with allergic constitution are exposed to allergens for the first time, the body will not produce allergic symptoms, but the immune system will recognize such substances as "harmful" and preserve memory. If they are exposed to this allergen again, their immune system will respond quickly, resulting in a series of allergic symptoms. Allergen "family" is huge and strange One of the reasons why allergy cannot be prevented is that the "family" of allergens is too large. "At present, there are hundreds of known allergens in clinic." According to Liu Ruiling, allergens can be introduced into the human body through four ways: inhalation allergens and injectable allergens. "Some food allergens can be avoided by paying more attention in life, such as peanut, milk, soybeans, eggs, seafood, etc. as long as they are strictly forbidden in their daily diet and do not eat, they will not cause allergic reactions. However, inhaled allergens, such as wind-borne pollen, can be transmitted by wind and enter the respiratory tract through breathing, so it is difficult to avoid contact." Liu Ruiling said. In addition to pollen, common inhalation allergens also include dust mites, molds and so on. There are also a wide range of contact allergens, including nickel chromium cobalt metal, hair dye, fabric dye, perfume, preservative, rubber additive and so on. In addition to these common allergens, there are many strange allergens. It is reported that an 11 year old boy died of severe allergic diseases due to the fishy smell of cooking fish. Another British woman is allergic to water. Her skin blisters as soon as she touches water. Allergy seems to have no signs, but it is "premeditated" Many people may encounter a substance that can "coexist peacefully" in life, and suddenly one day they begin to be allergic to it. What's the matter? In this regard, Liu Ruiling said that before explaining this situation, we should first talk about the mechanism of hypoallergeny. "As we said earlier, after human exposure to allergens, the human body begins to be in an asymptomatic incubation period. This stage is called sensitization stage. After re exposure to allergens, clinical symptoms will appear. This stage is called sensitization stage." She said. Some people are in the sensitization stage and have not been ill. However, due to repeated and constant exposure to allergens, such as traveling to the seaside and consuming a large amount of fish, shrimp and other seafood every day, the body may enter the sensitization stage from the sensitization stage, so people who were not allergic to seafood showed allergic reactions to seafood. In addition, some people may also have allergic reactions when they are exercising, drinking, undergoing surgery, suffering from major diseases or great emotional stress. Sometimes, we will find that some people are only slightly red and itchy when they are allergic to the same substance, others have tears, and even cough, asthma and other symptoms. Why does the degree of allergy vary from person to person? Liu Ruiling said that generally speaking, the severity of allergic symptoms is related to the activity of allergen substances, the amount of allergens absorbed by the human body and the sensitivity of patients to allergens. Liu Ruiling pointed out that avoiding contact with allergens is the best way to prevent and treat allergies. People with allergic diseases should know which substances they are allergic to and try to avoid contact or exposure to allergens; At the same time, anti allergic and anti-inflammatory drugs and desensitization treatment can also be used to control symptoms. (Xinhua News Agency)